Loud speaker, gramophone, and other sound recording or reproducing apparatus



Oct. 30, 1928. 1,689,997

' C. M. DE C. DE-LA BOURDONNAIS LOUD SPEAKER, GRAHOPHONE AND OTHER SOUND RECORDING OR REPRQDUING APPARATUS Filed July 19, 1926 2 Sheets-Sheet 1 Oct. 30, 1928. 1,689,997

C. M. DE C. DE LA BOURDONNAIS LOUD SPEAKER, GRAMQPHONE, AND OTHER SOUND RECORDING OR REPRODUCING APPARATUS Filed July 19, 1926 2 Sheets-Sheet 2 Wwg Patented 0a. so, 1928.

UNITED STATES PATENT OFFICE.

cmnnns mm: m: GHENAIJ m u nounnomurs, or Lovmrroa won, Nma'o'rm,

' ENGLAND.

LOUD SPEAKER, GBLKOPHONE, AN D OTHER SOUND RECORDING OB REYBODUGIHG APPARATUS.

Application fled July 18, 1928, Serial No. 128,506, and in Great Britain July 88, 1925. I

This invention relates to loud-speakers, gramophones, or the like, that is to say analogous sound-recording or reproducm paratus in general, and ithas for its ob ect so to construct these apparatus that they may faithfully reproduce all sounds over an extended range.

It refers to apparatus of the kind comprisin a large resonance chamber having a diap ragm (perforated or not) arranged in front of said chamber in such a manner as to utilize the sound waves from both its outer and inner sides.

According to my invention the large resonance chamber is provided with a short, shallow, 0r dish-like horn, in order to increase the volume and provide a slight directional effect. This also provides for the necessary amount of damping to prevent any ten denc of such a large diaphragm to ?boom on the lower frequencies of audible sound.

The horn and the resonance chamber may, if

preferred, be formed in one, and the diaphragm would .then be suitably supported in front of, or within, the said chamber, and may have an annular space, aperture, or gap around it for the passage ofthe vibrations.

In a loud-speaker embodying my invention the lar resonance chamber, which is made of woo or any other suitable material, and which may or may not be perforated, has

placed over, or upon, it, 'alarge diaphra m (or any suitable shape and material) ,andtis latter is operated, say b the centre-pull method, either electrlcal y, or mechanically an aperture, or apertures, bein provided, if desired, to permlt both the e cient vibration of the centre part of the diaphragm and the ready communication of the vibrations of the air enclosed within the resonance chamber, to the outer air.

The diaphragm may be operated from either the inside or the outside of the resonance chamber. A suitable diameter for said chamber and diaphragm is about fifteen inches, but this measurement must, however, be goverened by considerations of utility and yolume required, and may be varied accordly. I in order that the invention may be clearly understood, and readily carried into eifect, reference will now be had, by way of example, to the accom anying drawings in which Fig. 1 is a ront vlew, and

Fig. 2 is a vertical section of an arrange- 66 ment in which the short, shallow, or dish-like horn and large resonance chamber are formed in one, a more or less annular space, aperture, or vent being left around the edge of the diaphragm.

Fig. 3 is a front view of a similar arrangement, but in which the edge of the dia hragm is attached to the horn, and a circum erential ring of apertures is provided for the passage of the vibrations.

Fig. 4 is a fragmentary sectional View thrlough one of such apertures, on a larger sca e.

Fi 5 is a vertical section of a modification in w ich the resonance chamber is partly 70 a separate structure secured in theback of the horn.

Referrin more particularly to the example shown in igs. 1 and 2:

(1 represents the resonance chamber whilst b shows the diaphragm, which is carried by suitable supports 0, such as small wood blocks, secured to the adjacent part of the horn d, and to the back plate or rear cover d of the resonance chamber.

e is the receiver for operating the diaphragm. This receiver is carried on the said ack or rear cover (1 and is connected with the centre of the diaphragm by a light rod 0 or in any convenient manner.

The shallow-or dish-like horn (1 may be of octagonal shape asshown, and is formed of woo wood-pulp, or other suitable material, as may also be the diaphragm itself. The apparatus is supported by a short pillar f secured to the ack d and mounted on a pedestal f.

The passage of the vibrations from the resonance chamber or space a, behind the dia phragm, is provided for by an approximately annular opening, gap, or aperture, left between the edge of the diaphragm and the inner wall of the born. The extent or outer limit of this gap or opening is indicated in Fig. 1 by the dotted line b", which latter marks the line'where the diaphragm would, if it were lar e enough, meet the octagonal side walls of t e horn.

The small supports which carry the diaphragm are eight in number in the present example, to correspond to the number of sides of the horn. As they only take up very little space they do not interfere with the emission gap or vent (bounded by the line b") and sup" plement those emitted from the front of the diaphragm.

The horn with the back d is substantially a truncated cone open at the base.

Thus the volume of the sound depends not only on the vibrations emitted from the front of the diaphragm, but also, to an approximately equal extent, on those set up at thev rear of the diaphragm in the resonance chamber.

In the arrangement shown in Figs. 3 and 4, practically the same construction is followed in principle, but the diaphragm is extended right across the inside of the horn arallel to the back (1 and is secured thereto y a small lip or flange suitable apertures I) being provided around it near its edge for the passage of the sound waves coming from the resonance chamber.

In the arrangement shown in Fig. 5, the

diaphragm b is supported across a flanged ring or frame a which may be of truncated conical form, and which is secured to the back d of the resonance chamber, and is provided with holes or vents b all roundit for the escape of the sound waves, a suitable gap of clearance being left all round between it and the inner wall of the horn.

Furthermore, the walls of the ring a may be made so thin as to communicate the vibrations from the back of the diaphragm to the outer air without the use of the holes.

In some cases the resonance chamber itself may be perforated either round the sides, or at the back, or both, as desired, for the freer emission of the sound.

It will be readily understood that a soundrecording or reproducing apparatus such as a loud-speaker, gramophone, or the like, according to this invention, approximately doubles the volume of sound obtainable from any given diaphragm, in that the sound waves emitted from the back thereof are reflected outwards together with those coming 01f the front of the diaphragm. Care is of course taken that the diaphragm b is situated at such a distance from the. back d of the resonance chamber that the reflected sound waves are sufiieiently in phase with those coming ofl the front to preserve clarity of reproduction in conjunction with the increased volume obtained.

Although, in the examples illustrated, the horn has a uniform taper which extends to the back plate or sound-reflector d yet it will be readily understood that this is not a necessary arrangement, as the resonance chamber may be a cylindrical box fitted behind the tapered part of the horn, with the diaphragm extending across it at thejunction of the two.

Obviously, the above arrangements may be modified in various ways in carrying the invention into practice without departing from the nature thereof. 4

Having now described my said invention, what I claim is 1. A loud speaker comprising a truncated conical horn closed at the truncated end thereof, a diaphragm supported parallel to the closed end and forming therewith a resonance chamber which is open to the open end of the horn, and means for vibrating the diaphragm.

2. A loud speaker includin a diaphragm, means to vibrate the same, an a shallow open vessel-like member, the bottom of whi h is flat and is in spaced relation to the diaphragm and forming therewith a resonance chamber, said chamber being open to the open end of the vessel.

3. A loudspeaker including a diaphragm, means to vibrate the same, and a shallow open vessel-like member, the bottom of which is flat and is in spaced relation ,to the diaphragm and forming therewith a resonance chamber, said chamber-being open peripherally to the open end of the vesse 4. A loud speaker comprising a truncated conical horn closed at the truncated end thereof, a plurality of supports attached to the walls thereof adjacent the bottom and in spaced relation peripherally thereof, a diaphragm supported by the latter and provid ing with the closed end of the born a reso nance-chamber, said resonance chamber being open at the periphery of the diaphragm and between the supports, and means for vibrating the diaphragm.

In witness whereof, I have hereunto signed my name.

CHARLES MAHE ile CHENAL dc ll BOURDONNAIS, Prince de Milli. 

